Acoustic performance of lighter window laminates is below that of thicker laminates of equivalent construction, which permits the passage of sound and noise through the laminate. The frequency of this sound or noise occurs from approximately 1,000 Hz to 10,000 Hz. This is relevant for vehicle windows, as this sound or noise is in the range of human speech and is very prominent and distracting to passengers. Therefore, it is desirable to have a material that will absorb and dissipate mechanical frequencies in this range so that external sound or noise can be attenuated.
Efforts have been made to address noise attenuation. For example, improved noise attenuation has been achieved with an acoustic grade of polyvinyl butyral PVB. Acoustic PVB (APVB) consists of three layers of material: two outer layers of standard PVB (SPVB) and a core layer of PVB in the middle that is plasticized with triethylene glycol bis-2-ethylhexanoate. However, even acoustic grade of PVB is not sufficient for some window laminate designs and therefore even greater noise attenuation is needed.
In many transportation applications, fuel economy is a function of vehicle weight. It is desirable, therefore, to reduce the weight of laminates for such applications without compromising their strength and sound-attenuating properties. In view of the foregoing, thinner laminates that possess or exceed the sound-damping, durability, and breakage performance properties associated with thicker, heavier laminates are desirable.